Being debited for months now since inception for Data that i can't access and MTN won't help

Good Day, last week I had a complain regarding my contract with MTN and the terrible service I'm currently receiving. Someone called me to assist and said they will call me back to solve the matter. Can you believe no one has called me back yet. So I'm busy paying for data I'm not using cause I can't access it, and forfeiting it at the sometime. The worst of all an incorrect amount is being debited.

I want to terminate my contract with MTN and I expect a refund for all the money that has been debited for the data I can't even access. I really to regret taking a contract with this network.